Genetic testing can be both a boon and a curse, experts say, since more information often means more, and often confusing, options.

Genes can be remarkably loose-lipped. Mutations can expose hidden disease processes, and the products that emerge from the DNA code they spell out — enzymes, hormones, proteins and the like — are also giveaways for what’s going on in the body.

And these molecular motormouths are particularly useful when it comes to pinpointing diseases like cancer. At the most basic level, it’s possible to identify certain genes, or aberrations in genes, that people inherit from their families and confer a higher risk of developing the disease.

That’s the case with BRCA1 and BRCA2, two genes that normally work to keep cells from growing abnormally. Some mutations in the DNA that encodes them, however, give tumors relatively free reign to divide out of control. Women like Angelina Jolie, who inherited the harmful mutations, can have anywhere from a 40% to 90% increased risk of developing breast cancer in their lifetime (not all BRCA mutations are created equal; some are more dangerous than others). That’s a fivefold increased risk of cancer compared with women without the mutations.

So for the 1% of women with breast cancer who test positive for a BRCA mutation, doctors say it’s not unreasonable to consider something as radical as a double mastectomy — before they even find any signs of cancer. “It’s one of the truly unique situations where most medical professionals would say if a woman chose to have both breasts removed, it’s a pretty reasonable thing to do,” says Dr. Eric Winer, of the Dana-Farber Cancer Institute.

Prophylactic double mastectomies, as they are called, are one of the most common options that women in the U.S. choose if they are diagnosed with BRCA-based breast cancer. It’s a way to prevent disease before it even occurs, but it’s not the only strategy available to patients; women can opt to have regular MRI screenings to detect the first signs of a tumor, and then decide whether they want to remove their breasts entirely or just a portion of breast tissue at that time. They can also take tamoxifen, a synthetic anticancer drug that recent studies showed can cut the risk of developing breast cancer by 40% to 50%.

There’s also a surgery that seems completely unrelated to breast cancer but that can have a dramatic effect on prevalence of the disease, particularly for women who are BRCA-positive. Not only do the mutations increase the risk of breast cancer, but they can also boost the odds of ovarian cancer from 1.5% among women without the aberrations to anywhere from 15% to 40% for women who do. It’s this risk that’s of greater concern to cancer doctors, since there are no effective ways of screening for ovarian tumors, and most women who are diagnosed with the disease have already progressed to advances stages. Surgically removing the ovaries and fallopian tubes can significantly lower the risk of both breast and ovarian cancers; in a 2002 study, Dr. Kenneth Offit, chief of clinical genetics at the Memorial Sloan-Kettering Cancer Center, and his colleagues first reported that 3% of women undergoing the oophorectomy surgery developed breast cancer after about two years, compared with 11% of women who did not have the procedure.

Removing the breasts, however, does not seem to have an impact on the incidence of ovarian cancer, which is why most doctors recommend surgery to remove the ovaries first, to address the more pressing need of lowering a woman’s risk of developing ovarian cancer. “We don’t have good screening strategies for ovarian cancer, so it makes sense to try to be aggressive in preventing the development of the disease,” says Dr. Isabelle Bedrosian, associate professor of surgical oncology at MD Anderson Cancer Center.

But Jolie, like many women, decided to be proactive and remove her breasts first, and that decision may be driven largely by social and cultural factors. Living with the specter of cancer goes against the American take-action mentality for which watchful waiting is anathema, and that could be why the U.S. and Canada lead the world in preventive double mastectomies as a treatment for breast cancer. In certain parts of Europe, however, very few women, even those who test positive for BRCA, choose to have the prophylactic surgery. “If you go to Paris and the Institute Curie and you have a BRCA mutation, the chances of having preventive breast surgery are almost zero,” says Offit. “Whereas in northern Europe the rate is close to 100%.”

In the U.S., about 36% of women who test positive for BRCA choose to get prophylactic double mastectomies, according to a recent study by researchers at the Women’s College Research Institute in Toronto. Without any additional information to help them gauge exactly what their chances of developing cancer are, the peace of mind that comes from lowering their risk by any means possible may be worth losing their breasts. Jolie said her surgery dropped her chances of developing cancer from 87% to 5%.

Offit, who discovered the BRCA2 mutation, is hoping to refine that decisionmaking process with some stronger scientific data. He recently zeroed in on an additional genetic test that could narrow the 40% to 90% increased risk that the BRCA test confers. “If you knew your risk was closer to 90%, then you might be more inclined to have a mastectomy than if your risk was on the lower side,” he says. “It would be an additional genetic modifier to pinpoint the risk and make it more precise.” He and his team have launched a study to determine if the additional genetic information changes women’s decisions to have mastectomies by providing them with a stronger assessment of their risk of developing cancer.

Such objective criteria, however, may not be able to sway women’s perceptions and decisions about cancer care, which are heavily influenced by the experiences of their relatives with the disease. Losing sisters or a mother at an early age to breast cancer might make a patient more likely to decide to remove her breasts prophylactically, whereas having a mother or an aunt who opted to remove the lump and a small area of breast tissue tends to bias patients toward less radical therapies. Meanwhile, those who do not test positive for the BRCA mutations but are diagnosed with breast cancer may choose to have mastectomies in order to avoid any possibility of developing a tumor.

And that’s frustrating for many cancer doctors, since recent research suggests that a lot of these mastectomies may not be necessary. European scientists found that among a group of 701 breast-cancer patients, survival for 20 years after diagnosis was the same for women who chose to have only the tumor and a small portion of breast tissue removed as it was for women who decided to have a mastectomy.

Jolie’s experience, and her decision, while certainly not novel, is likely to raise awareness about genetic testing and its role in diagnosing and treating cancer. “I think we will see an increase over the next months for sure in genetic testing for breast cancer,” says Rebecca Nagy, a genetic counselor at Ohio State University’s medical center and president of the National Society of Genetic Counselors. “But what’s important to know is that it’s not appropriate to test everybody.”

For women like Jolie who have not had breast cancer yet, doctors will consider family history to determine how likely it is that she carries a BRCA mutation; red flags include having relatives with breast cancer, or unusual cancers, as well as those who developed the disease at an early age. Only then will doctors write an order for the test, which establishes its medical necessity since the woman is likely to be at higher-than-average risk of developing cancer, and refer the patient to a genetic counselor. The counselor is likely to do a more thorough investigation of the patient’s family history to determine whether the test would help guide treatment or not be of much added value. “We look to see if the genetic testing will give the patient the answers they are looking for or whether they will muddy the waters,” says Nagy. “And if we do decide to test, we need to decide which test is the right one.”

Making that decision will become increasingly challenging for genetic counselors like Nagy, since new tests that can prompt tumor genes to spill their secrets will continue to flood the clinic. For women with the BRCA mutations, the path forward is relatively straightforward; their genetic makeup puts them at increased risk of developing breast and ovarian cancers, and they have defined strategies for lowering that risk. For the vast majority of women, however, their risk will fall somewhere between the average risk of the disease and the higher vulnerability afforded by the BRCA mutations. “What is coming down the pipeline are a range of additional tests that will increase the panel of genes to be explored and looked at,” says Bedrosian. “For most women, their breast cancer is not caused by BRCA but does run in families, so what genes are responsible? We will slowly unfold what those genes are.” And that information could guide more women toward treatments that are appropriate for them — and help them to preserve their breasts where possible.